The present invention relates to a storage system for use in a computer system. More particularly, the invention relates to a method and apparatus for managing a volume configuration and failure, on a storage area network (hereinafter, referred to as SAN) such that the real volume provided from a storage system is to be provided as a virtual volume to a host computer through a volume virtualization function of a virtualization device.
(1) SAN
Recently, there is a growing spread of SANs, the networks exclusive for storage inputs/outputs integrated by separating the storage devices from the host computers. By introducing the SAN, it is possible to realize high-speed data transfer, high extensibility and usability for the storage system, and effective utilization of storage resources.
(2) SAN Management
The SAN-based high extensibility of a storage system allows a plurality of vendor devices (host computers, switches, storage devices) to coexist on the SAN. SAN management is required in order to operate such a SAN without shutdown. With respect to SAN management, particularly important is operation status monitoring of the devices to be connected to the SAN, that forms a basis of routine operations. The software, for monitoring the status of SAN operation, is hereinafter referred to as a SAN manager.
The SAN manager possesses two major functions, namely a configuration management function and a failure monitoring function. The configuration management function is a function to acquire information at regular intervals from the management agents existing in the devices connected to the SAN, detect a physical connection relationship (topology) over the SAN from the acquired information, and visualize at all times the newest topology to be supplied to the user of the SAN manager, i.e. to the SAN administrator.
The failure monitoring function is a function to grasp an event occurrence, such as a failure or a performance decrease, depending upon the event notification as to hardware malfunction and performance decrease issued from the devices connected to the SAN or the device information periodically acquired from the management agents existing in the devices. The occurrence of such an event is notified to the SAN administrator.
By virtue of these two functions, the SAN administrator can manage the device operation status in a centralized fashion by use of the SAN manager. This can reduce the operation cost, including personnel reduction for the SAN administrator.
(3) Virtualization Device
There is a virtual volume technology as an art to manage the storage over the SAN. The virtual volume technology is disclosed in GB-A-2351375, which discloses that the device called a storage host computer possesses the following two functions:
1) The function of managing a volume (hereinafter, real volume) as a storage domain in a storage medium being included in each storage device connected to the storage host computer and producing a volume pool; and
2) The function of producing a virtual volume based on one or more real volumes of the volume pool and converting sequentially the I/O access from the host computer to the virtual volume into an I/O request for real volume thereby making a response to the I/O from the host computer.
The device having these two functions is hereinafter referred to as a virtualization device. By introducing the virtualization device onto the SAN, the volume allocation onto the host computer is centralized by means of the virtual volume thus eliminating the necessity of being conscious of the physical configuration of the storage devices connected to the virtualization device. Namely, the SAN administrator is allowed to allocate volumes in a centralized manner.